The proceedings of two recent NIH-sponsored workshops have expressed concern over changing patterns of systemic fluoride exposure, as evidenced by increases in the prevalence and severity of fluorosis. It was agreed that there is an important need to monitor shifts in exposure, and that improved and more practical methods of measuring cumulative systemic exposure are urgently needed. The project described in this application will determine to what extent F- concentrations ([F-]) in dentin collected from exfoliated primary teeth (EPT) can serve as an accurate and useful marker to monitor cumulative systemic F- exposure during infancy and childhood. The Specific Aims are: (l) Using the rat molar as a model system, to define the relationship between F- uptake in dentin during the period of primary dentin deposition and after the completion of primary deposition. (2) To determine the [F-] profile in dentin from EPT, proceeding from the dentin-enamel junction to the pulpal surface using SIMS, and to relate these data to information from respective fluoride exposure histories (FEH), and to the caries and fluorosis index scores. (3) To investigate the relationships between [F-] in dentin (obtained by chemical analysis) from EPT, and the respective systemic F- exposure as estimated from fluoride exposure histories, fluorosis index scores taken from the permanent teeth, and caries index scores. The usefulness of the field- collection adaptations of the method will be evaluated. The findings generated from Specific Aims #1 and #2 will provide information on biologic parameters important to interpretation of the findings to be obtained from the clinical-epidemiological study described in Specific Aim #3. We hypothesize that the results of this project will show that [F-] in dentin from EPT can be used as an accurate and usefully applied marker to monitor cumulative systemic F- exposure during infancy and childhood.